Thread severing device for sewing machines



March 27, 1945. p ENOS 2,372,318

THREAD SEVERING DEVICE FOR SEWING MACHINES Filed Aug. 28, 1945 Patented Mar. 27, 1945 THREAD SEVERING DEVICE FOR SEWING MACHINES John P. Enos, Union, N. J assignor to The Singer Manufacturing Company, Elizabeth, N. J a corporation of New Jersey Application August 28, 1943, Serial No. 500,405

Claims.

This invention relates to thread-severing de-' vices for sewing machines and, more particularly, to devices for severing the stitching thread or threads between successively stitched articles.

The presentinvention comprises an improvement in the thread-severing device forming the subject of my prior U. S. Patent No. 2,318,843, May l1, 1943, and has for its object to provide means which may be conveniently brought into effective action during the operation of the machine for severing the stitching threads directly adjacent to or at any desired distance from either the beginning or finishing ends of the work.

The invention comprises complemental threadsevering elements disposed at opposite face sides of the work and normally held out of cooperative thread-severing relation independently of the work; one of said thread-severing elements being continuously actuated during the operation of the machine, and said elements being shiftable relatively to each other at will into cooperative thread-severing relation in the absence of workarticles between the severing elements.

In the accompanying drawing, which illustrates a preferred embodiment of the invention, Fig. 1 is a view in elevation, partly in section, of a portion of the left hand end of a sewing machine containing the present improvement. Fig. 2 is an enlarged bottom plan view of the presserfoot and of the upper cutter-block associated therewith. Fig. 3 is a rear elevation of the presser-foot of the machine and of the associated cutter attachment, including the lower end portion of the presser-bar. Fig. 4 is a front elevation of the parts shown in Fig. 3. Fig. 5 is a side elevation of the presser-foot and cutter attachment as viewed from the side opposite to that shown in Fig. 1; the cutter-block and the actuating lever therefor being also shown in dotted lines in the operative position of the cutter-block. Fig. 6 is an enlarged fragmentary vertical section of the presser-foot, cutter-block. throat-plate and feed-dog of the machine; the cutter-block being depressed into position for coaction with the feed-dog in severing the threadchain. Fig. '7 is a vertical section taken substantially on the line 'l'l of Fig. 6.

The sewing machine in part illustrated in the drawing has the usual frame including a worksupporting bed-plate l8 and a bracket-arm head II overhanging the bed-plate. Journaled for vertical reciprocation in the bracket-arm head II is a needle-bar l2 carrying a needle l3.

Complemental to the needle I3 in the formation of lock-stitches isa loop-taker [4 which, in the present case, is in the form of a horizontalaxis rotary hook adapted to cast loops of needlethread a about a mass of under thread b contained in a thread-carrier l5 suitably journaled in the loop-taker and restrained against rota-- tion therewith. The present invention, however, is not limited to any particular form of looper or loop-taker mechanism.

Suitably secured upon the bed-plate I0 is a throat-plate l6 having a needle-aperture I1 and a plurality of substantially parallel feedslots I8. Operating through the feed-slots l8 of the throat-plate are the toothed sections I9, and 2| of a feed-dog 22. The feed-dog 22 is suitably secured upon a horizontally disposed feed-bar 23, of which the rearward end is pivotally connected to the upper end of a vertically disposed rocker 24 carried by a feed-advance rock-shaft 25. At its forward end, the feed-bar 23 is operatively connected to a crank-arm 21 of a feed-lift rock-shaft 28. The rock-shafts 25 and 28 may be supported and actuated in any suitable manner (not shown) to impart the conventional four-motion movements to the feeddog 22.

The middle section 20 of the feed-dog is disposed in a vertical plane containing the line of scam formation and entirely rearwardly of thepath of reciprocation of the needle l3, whereby the teeth of that section not only engage and feed the stitched work but also function to feed the concatenated stitching threads a, b in the absence of work. The rear tooth 20 of the toothed section 20 of the feed-dog is enlarged lengthwise and Widthwise to provide a horizontally flattened upper face or land and to extend laterally beyond the opposite sides of the forward portion of the section 2ll. The upper rear edge of the feed-dog tooth 20' is formed into a sharpened cutting edge 29 by hollow grinding the rear face of the tooth 20, as illustrated more particularly in Fig. 6 of the drawing. ;In its preferred form, the cutting edge 29 is horizontally normal to the line of feed.

Opposed to the feed-dog 22 is a presser-foot having a work-engaging sole-plate 30 and a shank 3| detachably secured by a screw 32 to the lower end of a vertically disposed presserbar 33. The presser-bar 33 is journaled for endwise movement in the frame-head II and is spring-depressed in any usual or suitable manner (not shown). The sole-plate 30 of the presser-foot is conventionally provided with a needle-aperture 34 in vertical alinement with the throat-plate needle-aperture I1.

Rising vertically from the presser-foot soleplate 30, rearwardly of the needle-aperture 34 therein, are two guide-posts 35 and 36 disposed abreast with respect to the line of seam formation. The guide-posts 35 and 38 are slidingly disposed in vertically apertured bosses 31 and 38 formed integral with and at the forward portion of the presser-foot shank 3|. A bent wire spring 39 is secured between its ends upon the front face of the presser-foot shank 3| by a screw 49. The opposite free ends of the spring 39 pass through apertures provided in the upper ends of the respective guide-posts 35 and 36, thereby yieldingly to depress the sole-plate 30 to a limited extent relatively to the presser-foot shank.

The under face of the presser-foot-shank 3| is partly cut away to provide clearance for vertical movement of the sole-plate 30 and to form a presser-foot heel portion 4| which is integral with the shank 3| and is disposed rearwardly of the sole-plate 30, in close proximity to said sole-plate. The heel-portion 4| has its under or work-engaging face normally disposed in substantially the horizontal plane containing the tread face of the sole-plate 30. This construction provides for limited work-responsive movements of the soleplate 30 without affecting the presser-foot heelportion 4|, whereby the feeding of the work or the thread-chain rearwardly of the needle will continue to be effective independently of limited lifting movements of the sole-plate 30.

The heel-portion 4| of the presser-foot is rigidly provided medianly of the width thereof with a relatively narrow extension-piece 42 opposed to the rearward portion of the threadchain advancing feed-dog section 20. The upper face of the extension-piece 42 is rearwardly beveled and the under face thereof is concavely recessed in the line of seam formation to provide a shallow thread-clearance groove 43 which preferably extends forwardly through the heel-portion 4| said groove 43 being preferably concave widthwise of the extension-piece 42 and having the crest of its concavity disposed substantially in the vertical plane containing the line of seam formation.

The lower portion of the presser-foot shank 3| has opposed flattened side faces and is provided with a vertically elongated slot 44 (Fig. 6). Extending through the slot 44 crosswise of the line of scam formation is a horizontally disposed pivot-pin 45. Adjustably threaded downwardly into the presser-foot shank 3|, medianly of the width of said shank, is a limit-screw 46 extending into the shank-slot 44 and adapted, adjustably, to limit upward movement of the pivot-pin 45 in the slot 44. This arrangement provides for floating movement of th pivot-pin 45. The limit-screw 46 is secured in adjusted position by a set-screw 41 threaded into the shank 3|.

Hung upon the opposite ends of the pivot-pin 45 are the laterally spaced and forwardly extending arms 48 of a cutter-block carrier 49 disposed rearwardly' of the presser-foot. The carrier 49 is longitudinally recessed to provide a downwardly open T-shaped guideway 50. Slidably disposed in the guide-way 50, for adjustment toward and from the path of needle-reciprocation, is an upper thread-severing member complemental to the lower thread-severing member 28'. The upper thread-severing member comprises a cutter-block which, together with the means employed for adjusting and securing the cutter-block in set position upon the carrier, corresponds substantially with the cutter-block disposed in my prior U. S. Patent No. 2,318,843 hereinbefore mentioned. The under face of the cutter-block 5| is stepped to provide a cutting edge 52 which extends crosswise of the line of seam formation and which cutting edge, in a-depressed position of the cutter-block carrier 49, is disposed in thread-shearing relation to the cutting-edge 29 of the. feed-dog. As illustrated in the drawing. the upper cutting-edge 52 is disposed slightly "rearwardly of thepresser-foot extension-piece 42.

Mounted upon the presser-bar 33 and secured thereupon by screws 53 is a bracket 64 provided with a depending supporting-plate 55 which is disposed to the right of the presser-bar 33. Pivotally mounted upon the supporting-plate 55 is a two-armed hand-lever 56 fulcrumed between its ends upon a screw 51 for pivotal movement about a horizontal axis extending transversely of the line of seam formation. The upper arm of the hand-lever 56 is bent laterally to provide a finger-piece 58 which extends to the right of the hand-lever 56 in a direction generally crosswise of the line of seam formation. The upper arm of the hand-lever 56 is biased forwardly by a spring 59 secured to the supporting-plate 55 by a stopscrew 60 disposed rearwardly of the hand-lever 56 and in position for engagement by the lower arm of said hand-lever, thereby to limit pivotal movement of the hand-lever 56 under the action Of the spring 59. Movement of the hand-lever 56, in opposition to the spring 59, is limited by a stop-plate 6| adjustably secured upon the supporting-plate 55 by a screw 62; said stop-plate 6| being provided at its forward end with an ear 63 disposed rearwardly of the hand-lever 56 for engagement by the upperarm oi' the hand-lever.

The free end portion of the lower arm of the hand-lever 56 is bent laterally and downwardly to provide a depending lip 64. This lip 64 of the hand-lever overlies an ear 65 extending rearwardly from the upper portion of the cutter-block carrier 49; said ear 65 being disposed substantially medianly of the width of the carrier 49. The hand-lever lip 64 is yieldingly held in constant engagement with the upper face of the carrier-ear 65 by a substantially U-shaped spring 66. One end of the spring 66 is secured to the handlever 56 by a screw 61 and the other end of said spring is formed into a wire-loop 68 disposed in engagement with the under face of the carrierear 65. The spring 66 functions to swing the cutter-block carrier 49 upwardly upon movement of the hand-lever 56 in response to the action of the spring 59.

Fig. 6 of the drawing shows the work w disposed under the presser-foot sole-plate 30 short of the presser-foot heel 4|; the work-engaging face 'of the sole-plate 30 being shown as raised by the work relatively to the heel 4|, and the feed-dog section 20 being shown as coacting with the heel of the presser-foot in feeding the concatenated threads a and b extending from the rearward end of the work. The thread-receiving groove 43 of the heel 4| at this time assists in maintaining the concatenated threads a, b, in substantially the line of seam formation, whereby said threads are advanced into position for severance thereof. The cutter-block carrier 49 is shown in Fig. 6 in a depressed position thereof attained by manually rocking the upper arm of the hand-lever 56 rearwardly. In the continued rearward movement of the feed-dog 22 from the position thereof shown in Fig. 6, the cuttingedge 29 of the feed-dog section 20 is brought into thread-shearing relation with the cutting-edge 52 of the cutter-block 5|. This shearing relation of the tWo cutting edges 29 and 52 is attained smoothly and with certainty by reason of the fact that the cutting edge 52 is disposed-in the plane of the under face of the cutter-block carrier 49.

The described construction presents the advantage of providing for severing the threadchain either close to or at any desired distance from the work, either or both at the beginning and finishing ends of the work. When the handlever 58 is released by the operator, the spring 59 functions to retract said hand-lever, thereby pivotally lifting the cutter-block carrier 49,

through the spring-member 66, into an inoperative position of the upper cutting edge 52 above the plane of the work-engaging face of the presser-foot heel I I, which inoperative position is normally maintained until it is again desired to sever the concatenated threads.

The groove 43 of the presser-foot heel-portion 4| has the further function of slightly relieving pressure upon the work at the point of engagement of the work by the rearward portion 01' the feed-dog 22, thereby reducing to a negligible extent any possibility of mutilation of the work or the stitches by the lower cutting edge 29.

The finger-piece 58 of the hand-lever 56 is preferably located adjacent the presser-foot in the described position thereof, wherein it may be conveniently operated without interfering with the normal manipulation of tire work by the operator.

Having thus set forth the nature of the invention, what I claim herein is:

1. In a sewing machine having a work-support, stitch-forming mechanism including a reciprocatory thread-carrying needle, a work-advancing feed-dog operating through said work-support, a presser-foot opposed to said feed-dog and movable toward and from said work-support, a primary thread-severing element having a path of movement at the feed-dog face side of the work for severing the stitching thread between successively stitched articles, a complemental thread-severing element supported by and movabl relatively to said presser-foot toward and from the path of movement of said primary thread-severing element, a hand-lever pivotally supported for movement with said presser-foot and operatively connected for actuating said complemental thread-severing element, and spring means biasing said hand-lever into retracted position.

2. In a sewing machine, a work-support, a presser-foot opposed to said work-support, a presser-bar carrying said presser-foot and movable toward and from said work-support, a thread-severing element supported by said presser-foot for movement relatively to the presserfoot toward and from said work-support, said thread-severing element having a cutting edge disposed rearwardly of the path of needle-reciprocation and extending across the line of seam formation, a second thread-severing element having a path of movement at the face side of the work opposite the presser-foot face Side thereof, means for continuously actuating said second thread-severing element during the operation of the machine, a supporting bracket mounted upon said presser-bar, a hand-lever pivotally supported by said bracket, and operative connections with said hand-lever for moving the presser-foct supported thread-severing element toward and from the path of movement of said second thread-severing element.

3. In a sewing machine, a work-support, stitchforming mechanism including a reciprocatory thread-carrying needle, a presser-foot supported for movement toward and from said work-support, an upper thread-severing element disposed at the presser-foot side of said work-support for movement with said presser-foot, said upper thread-severing element having a cutting edge extending across the line of seam formation, a bracket supported for movement with said presser-foot, a two-armed lever fulcrumed upon said bracket and connected for shifting said upper.

thread-severing element to and from an operative position of said element upon actuation of said lever, stop-means limiting movement of said lever in opposite directions, a spring biasing said lever into-retracted position, a lower thread-severing member having a path of movement for threadsevering coaction with said upper thread-severing element in the operative position of said upper thread-severing element, and means for continuously actuating said lower thread-severing element during the operation of the machine.

4. In a sewing machine, a work-supp rt, stitch-forming mechanism including a reciproeatory thread-carrying needle, a presser-foot opposed to said work-support, a lower thread-severing element having a path of movement at the face side of the work opposite the presser-foot face side thereof, said lower thread-severing element having a cutting edge extending across the line of scam formation, means for continuously actuating said lower thread-severing element during the operation of the machine, an upper thread-severing element pivotally mounted upon said presser-foot, said upper thread-severing element being provided with a cutting edge disposed in the operative position of said upper element for thread-severing coaction with the cutting edge of said lower thread-severing element, a supporting bracket disposed adjacent said presser-foot, a hand-lever fulcrumed upon said bracket in position to bear downwardly upon said upper thread-severing element upon movement of said lever in one direction, spring means biasing said lever in the opposite direction into retracted position, and means connected to said lever for raising said upper thread-severing element into inoperative position upon movement of said lever into retracted position.

5. In a sewing machine, in combination, a work-support, a presser-foot opposed to and movable toward and from said work-support, a reciprocatory needle, a work-advancing feed-dog operating through said work-support, a primary thread-severing element carried by said feeddog and including a cutting-edge extending across the line of seam formation, a complemental thread-severing element pivotally supported by said presser-foot and provided with a. cutting edge extending across the line of scam formation rearwardly of the path of needlereciprocation. a pivotally mounted hand-lever disposed adjacent said presser-foot for downward engagement with said complemental thread-severing element in one direction of movement of said rand-lever, means carried by said handlever for retracting said complemental threadsevering element upon movement of said handlever in the opposite direction, spring means normally biasing said lever into a retracted position of said complemental thread-severing element, andstop means limiting movement of said complemental thread-severing element into both operative and retracted positions thereof.

JOHN P. ENOS. 

